Polyanhydrides with therapeutically useful degradation products

ABSTRACT

An aromatic polyanhydride comprising a repeating unit having the structure 
                         
is disclosed, wherein Ar and R are selected so that the aromatic polyanhydride hydrolyzes to form a therapeutic salicylate, another non-steroidal anti-inflammatory, an antifibrotic aminobenzoate, or a vasoconstricting phenylethanolamine. Implantable medical devices, such as scaffolding implants for tissue reconstruction, drug delivery systems prepared from the aromatic polyanhydrides, as well as therapeutic dosage forms and treatment methods are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.09/508,217, filed Jun. 18, 2004, now U.S. Pat. No. 7,122,615 whichclaims priority to International Patent Application No.PCT/US1998/018816 filed Sep. 10, 1998 and U.S. Provisional ApplicationNo. 60/058,328 filed Sep. 10, 1997, the entirety of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to biocompatible aromatic polyanhydrideshaving improved degradation properties and processability and uniquetherapeutic properties. In particular, the present invention relates toaromatic polyanhydrides produced from ortho-substituted bis-aromaticcarboxylic acid anhydrides. The present invention also relates toortho-substituted bis-aromatic dicarboxylic acids useful in thepreparation of the aromatic polyanhydrides of the present invention.

BACKGROUND ART

Biocompatible and biodegradable aromatic polyanhydrides are disclosed byU.S. Pat. Nos. 4,757,128 and 4,997,904. However, unless incorporatedinto a copolymer containing a more hydrophilic monomer, such as sebacicacid, the aromatic polyanhydrides of the prior art have slow degradationtimes as well as relatively insoluble degradation products. A majordrawback to the prior art aromatic polyanhydrides is their insolubilityin most organic solvents.

Biocompatible and biodegradable aromatic polyanhydrides prepared frompara-substituted bis-aromatic dicarboxylic acids are disclosed by U.S.Pat. No. 5,264,540. The para-substitution pattern results in higher meltand glass transition temperatures and decreased solubility, thusultimately making these para-substituted polymers difficult to process.

A need exists for biocompatible and biodegradable aromaticpolyanhydrides having improved degradation and processing properties, aswell as therapeutic utilities.

SUMMARY OF THE INVENTION

This need is met by the present invention. It has now been discoveredthat the preparation of aromatic polyanhydrides from ortho-substitutedbis-aromatic carboxylic acid anhydrides disrupts the crystallinity ofthe resulting polymer, enhancing solubility and processability, as wellas degradation properties. Therefore, according to one aspect of thepresent invention, an aromatic polyanhydride is provided having arepeated unit within the structure of Formula I:

wherein Ar is a substituted or unsubstituted aromatic ring and R is adifunctional organic moiety substituted on each Ar ortho to theanhydride group. Ar and R are preferably selected so that the hydrolysisproducts of the polyanhydrides have a chemical structure resemblingpharmaceutically-active materials, particularly salicyclates such asaspirin, non-steroidal anti-inflammatory naphthyl or phenyl propionatessuch as ibuprofen, ketoprofen, naproxen, and the like, or other aromaticanti-inflammatory compounds such as indomethacin, indoprofen, and thelike. In particular, Ar is preferably a phenyl group and R is preferably-Z₁-R₁-Z₁₋ in which R₁ is a difunctional moiety and both Z₁'s areindependently either an ether, ester, amide, anhydride, carbonate,urethane or sulfide groups. R₁ is preferably an alkylene groupcontaining from 1 to 20 carbon atoms, or a group with 2-20 carbon atomshaving a structure selected from (—CH₂—CH₂—O—)_(m),(—CH₂—CH₂—CH₂—O—)_(m), and (—CH₂—CHCH₃—O—)_(m).

Ortho-substituted bis-aromatic carboxylic acid anhydrides of the presentinvention are novel and non-obvious intermediate compounds havingutility in the preparation of the aromatic polyanhydrides of the presentinvention. Therefore, according to another aspect of the presentinvention, ortho-substituted bis-aromatic carboxylic acid anhydrides areprovided having the structure of Formula II:

wherein Ar and R, and the preferred species thereof, are the same asdescribed above with respect to Formula I and R is substituted on eachAr ortho to the anhydride group.

The present invention also includes ortho-substituted bis-aromaticdicarboxylic acids, which are novel and non-obvious intermediatecompounds having utility in the preparation of ortho-substitutedbis-aromatic carboxylic acid anhydrides. Therefore, according to anotheraspect of the present invention, an ortho-substituted bis-aromaticdicarboxylic acid is provided having the structure of HOOC—Ar—R—Ar—COOH,wherein Ar and R, and the preferred species thereof, are the same asdescribed above with respect to Formula I, and R is substituted on eachAr ortho to each carboxylic acid group.

The aromatic polyanhydrides of the present invention meet the need formoldable biocompatible biodegradable polymers. Therefore, the presentinvention also includes-implantable medical devices containing thearomatic polyanhydrides of the present invention. When Ar and R areselected so that the aromatic polyanhydride hydrolyzes to formtherapeutic salicyclates, the aromatic polyanhydrides have potentialuses as biocompatible, biodegradable scaffolding implants for tissuereconstruction in which the degradation products have anti-thrombogenicqualities.

In addition, the aromatic polyanhydrides that hydrolyze to formtherapeutic salicyclates have potential uses as anti-inflammatory dosageforms, including dosage forms for oral administration, particularly inthe treatment of digestive disorders, including bowel disorders such asinflammatory bowel disease, Crohn's disease, and the like. Ar and R mayalso be selected so that the aromatic polyanhydrides hydrolyze to formtherapeutic non-steroidal anti-inflammatory naphthyl and phenylpropionates that resemble compounds such as ibuprofen, ketoprofen,naproxen, and the like, and other aromatic anti-inflammatory compoundssuch as indomethacin, indoprofen, and the like.

Therefore, the present invention also includes a method for treatinginflammation by administering to a patient in need thereof a quantity ofthe aromatic polyanhydride of the present invention in which Ar and Rare selected so that aromatic polyanhydride hydrolyzes to formtherapeutic salicyclates at the site of inflammation in an amounteffective to relieve the inflammation. The aromatic polyanhydrides maybe administered orally. This is particularly useful in the treatment ofdigestive inflammation, such as inflammatory bowel disease, because thetherapeutic salicyclates are formed in the gastro-intestinal tract ofthe patient. Methods for treating inflammation with aromaticpolyanhydrides that hydrolyze to form therapeutic naphthyl or phenylpropionates are included in the present invention as well, as well asmethods for treating inflammtion with aromatic polyanhydrides thathydrolyze to form indomethacin or indoprofen.

The present invention therefore also includes anti-inflammatory oraldosage forms consisting essentially of the aromatic polyanhydrides ofthe present invention that hydrolyze to form therapeutic salicyclates ornaphthyl or phenyl propionates, or indomethacin or indoprofen, and apharmaceutically acceptable excipient. The oral dosage forms may furtherinclude a biologically or pharmaceutically active compound to beco-administered with the therapeutic degradation products.

Ar and R may also be selected so that the aromatic polyanhydrideshydrolyzes to form therapeutic antiulcerative drugs such as rosaprostol,therapeutic antifibrotic aminobenzoates and therapeutic vasoconstrictingphenylethanolamines and vasoconstricting drugs such as midodrine.Therefore, the present invention also includes a method for therapeutictreatment by administering to a patient in need thereof a quantity ofthe aromatic polyanhydride of the present invention in which Ar and Rare selected so that aromatic polyanhydride hydrolyzes to formrosaprostol, antifibrotic aminobenzoates, vasoconstrictingphenylethanolamines and midodrine. The present invention also includesoral dosage forms consisting essentially of the aromatic polyanhydridesof the present invention in which Ar and R are selected so that thearomatic polyanhydrides hydrolyze to form rosaprostol, antifibroticaminobenzoates, vasoconstricting phenylethanolamines and midodrine.

In another embodiment of the present invention, the aromaticpolyanhydrides are combined with a quantity of biologically orpharmaceutically active compound sufficient for effective site-specificor systemic drug delivery as described by Gutkowsky et al., J. Biomater.Res. 29, 811-21 (1995) and Hoffman, J. Controlled Release, 6, 297-305(1987). The biologically or pharmaceutically active compound may bephysically admixed, embedded or dispersed in the polymer matrix.Alternatively, derivatives of biologically and pharmaceutically activecompounds can be attached to repeating units of the polymers of thepresent invention by covalent bonds linked to an Ar ring or an R organicmoiety. This provides for sustained release of the biologically orpharmaceutically active compound.

Another aspect of the present invention provides a method forsite-specific or systemic drug delivery by implanting in the body of apatient in need thereof an implantable drug delivery device containing atherapeutically effective amount of a biologically or pharmaceuticallyactive compound in combination with an aromatic polyanhydride of thepresent invention.

A more complete appreciation of the invention and many more otherintended advantages can be readily obtained by reference to thefollowing detailed description of the preferred embodiments and claims,which disclose the principles of the invention and the best modes whichare presently contemplated for carrying them out.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides aromatic polyanhydrides with improveddegradation properties and processability having repeating units withthe structure of Formula I in which Ar and R are the same as describedabove with respect to Formula I. R preferably has a structure of-Z₁-R₁-Z₁-, in which R₁ is a difunctional organic moiety and both Z₁'sare difunctional moieties independently selected from ethers, esters,amides, anhydrides, urethanes, carbamates, carbonates, sulfides, and thelike. R₁ may be an alkylene group containing from 1 to 20, andpreferably 6, carbon atoms, or R₁ may be a group having from 2 to 30,and preferably 6, carbon atoms having a structure selected from(—CH₂—CH₂—O—)_(m), (—CH₂—CH₂—CH₂—O—)_(m), and (—CH₂—CHCH₃—O—)_(m), or R₁may have the structure -R₂-Z₂-R₃-, wherein R₂ and R₃ are independentlyalkylene groups containing from 1 to 19 carbon atoms or groups havingfrom 2 to 18 carbon atoms having a structure selected from(—CH₂—CH₂—O—)_(m), (—CH₂—CH₂—CH₂—O—)_(m), and (—CH₂—CHCH₃—O—)_(m), andZ₂ is selected from the difunctional moieties described above withrespect to Z₁.

Ar may be an alkylaryl group, in which a difunctional organic moiety ispositioned between each anhydride carbonyl group and the correspondingaromatic ring. Preferably, however, each carbonyl group is directlysubstituted on the corresponding aromatic ring.

Preferred polymers of the present invention have repeating units withthe structure of Formula I in which Ar is a phenyl ring and R isselected from -Z₁-(-CH₂-)_(n)-Z₁-, -Z(-CH₂—CH₂—O-)_(m)-Z₁-,-Z(-CH₂—CH₂—CH₂—O-)_(m)-Z₁-, and -Z(-CH₂—CHCH₃—O-)_(m)-Z₁-, wherein Z₁is an ether, ester or amide group and n is from 1 to 20 inclusive, andpreferably is 6, and m is selected so that R has from 2 to 20, andpreferably 6, carbon atoms.

The aromatic polyanhydrides of the present invention may be prepared bythe method described in Conix, Macromol. Synth., 2, 95-99 (1996), inwhich dicarboxylic acids are acetylated in an excess of acetic anhydrideat reflux temperatures followed by melt condensation of the resultingcarboxylic acid anhydride at 180° C. for 2-3 hours. The resultingpolymers are isolated by precipitation into diethyl ether from methylenechloride. The described process is essentially the conventional methodfor polymerizing bis-aromatic dicarboxylic acid anhydrides into aromaticpolyanhydrides.

Aromatic polyanhydrides in accordance with the present invention haveweight average molecular weights of at least about 1500 daltons, up toabout 35,000 daltons, calculated by Gel Permeation Chromatography (GPC)relative to narrow molecular weight polystyrene standards.

The aromatic polyanhydrides of the present invention are produced fromorth-substituted bis-aromatic carboxylic acid anhydrides having thestructure of Formula II in which Ar, R and the preferred species thereofare the same as described above with respect to Formula I. As notedabove, ortho-substituted bis-aromatic carboxylic acid anhydrides areprepared by acetylation of the corresponding ortho-substitutedbis-aromatic carboxylic acids in an excess of acetic anhydride at refluxtemperatures. The dicarboxylic acids have the structure of Formula III,wherein Ar, R and the preferred species thereof are the same asdescribed above with respect to Formula I.

The dicarboxylic acids are prepared by reacting a stiochiometric ratioof aromatic carboxylic acid having the structure Z₃-Ar—COOH and acompound having a structure Z₄-R-Z₄ wherein Ar is a substituted orunsubstituted aromatic ring on which Z₃ is substituted ortho to thecarboxylic acid group, R is a difunctional organic moiety and Z₃ and Z₄are functional groups selected to provide the linkage desired betweenthe difunctional organic moiety and the two aromatic rings.

Suitable Z₃ and Z₄ functional groups, and the manner in which they maybe reacted to produce the bis-aromatic dicarboxylic acids of the presentinvention, may be readily determined by those of ordinary skill in theart without undue experimentation. For example, for aromaticpolyanhydrides having the structure of Formula I in which Ar is a phenylgroup and R is —O—(CH₂—)₆—O—, the ortho-substituted bis-aromaticdicarboxylic acid starting material may be prepared by reactingo-salicylic acid with 1,6-dibromohexane.

The aromatic polyanhydrides of the present invention can be isolated byknown methods commonly employed in the field of synthetic polymers toproduce a variety of useful articles with valuable physical and chemicalproperties. The new polymers can be readily processed by solvent castingto yield films, coatings, dishes and sponges with different geometricshapes for design of various medical implants, and may also be processedby compression molding and extrusion. Medical implant applicationsinclude the use of aromatic polyanhydrides to form shaped articles suchas vascular graphs and stents, bone plates, sutures, implantablesensors, implantable drug delivery devices, stents for tissueregeneration, and other articles that decompose harmlessly within aknown time period.

The polymers of the present invention include aromatic polyanhydrideshaving a repeating unit with the structure of Formula I in which Ar andR are selected to provide aromatic polyanhydrides that hydrolyze to formtherapeutically useful salicyclates. As noted above, the salicyclatesmay be employed to treat inflammation, particularly digestiveinflammation such as inflammatory bowel disorders. Thus, implantable oringestible drug delivery devices of the present invention include oraldosage forms consisting essentially of the aromatic polyanhydrides ofthe present invention that hydrolyze to form therapeutic salicyclates,in combination with a pharmaceutically acceptable excipient. The oraldosage forms function to deliver salicyclates to the site ofinflammation, either directly, or by being absorbed into the bloodstreamfrom the digestive tract. The salicyclates may be supplemented withother therapeutic agents in the polymer matrix.

Examples of the therapeutic salicyclates include, but are not limitedto, thymotic acid, 4,4-sulfinyldinailine, 4-sulfanilamidosalicylic acid,sulfanilic acid, sulfanilylbenzylamine, sulfaloxic acid, succisulfone,salicylsulfuric acid, salsallate, salicylic alcohol, orthocaine,mesalamine, gentisic acid, enfenamic acid, cresotic acid, aminosalicylicacid, aminophenylacetic acid, acetylsalicylic acid, and the like. Theidentification of Ar and R moieties that provide aromatic polyanhydridesthat hydrolyze to form such therapeutically useful salicyclates can bereadily determined by those of ordinary skill in the art without undueexperimentation.

Ar and R may also be selected so that the aromatic polyanhydrideshydrolyze to form therapeutic non-steroidal anti-inflammatory phenyl andnaphthyl propionates, indomethacin and indoprofen. The identification ofAr and R moieties that provide aromatic polyanhydrides that hydrolyze toform such therapeutic anti-inflammatory compounds can also be readilydetermined by those of ordinary skill in the art without undueexperimentation.

Ar and R may also be selected so that the aromatic polyanhydrideshydrolyze to form other therapeutic compounds. For example, Ar and R maybe selected to provide an aromatic polyanhydride that hydrolyzes to formthe antiulcerative drug rosaprostol. Ar and R may also be selected toprovide aromatic polyanhydrides that hydrolyze to form antifibroticaminobenzoates. Ar and R may further be selected to providepolyanhydrides that hydrolyze to form the vasoconstricting drugmidodrine, as well as vasoconstricting phenylethanolamines. Again, theidentification of Ar and R moieties that provide aromatic polyanhydridesthat hydrolyze to form such therapeutic compounds can readily bedetermined by those of ordinary skill in the art without undueexperimentation.

Pharmaceutically acceptable excipients for oral administration are wellknown and include diluents such as lactose, sucrose, mannitol, sorbitol,cellulose, glycine, and the like, lubricants such as silica, talc,stearic acid and salts thereof, and the like, binders such as magnesiumaluminum silicate, starches such as corn starch, methyl cellulose, andthe like, and disintegrating agents such as starches, agar, and thelike, as well as dyestuffs, flavors and sweeteners. The dosage forms aremanufactured in a manner that is in itself well known, for example, bymeans of conventional mixing, granulating or dragee-making processes.

The quantity of aromatic polyanhydride that hydrolyzes to form an amountof therapeutic salicyclate effective to relieve inflammation can bereadily determined by those of ordinary skill in the art without undueexperimentation. The quantity essentially corresponds stiochiometricallyto the amount of salicyclate known to produce an effective treatment.Oral dosage forms of aromatic polyanhydrides that hydrolyze to formother therapeutic non-steroidal anti-inflammatory compounds and othertherapeutic compounds are prepared and administered in a similar manner.

The ortho-substituted aromatic polyanhydrides of the present inventionexhibit desirable adhesion to cell cultures. The disruption ofcrystallinity is believed to improve the attachment and growth of cellsand may facilitate specific interactions with proteins, peptides andcells. The aromatic polyanhydrides of the present invention are thususeful as scaffolding implants for tissue reconstruction. The polymersurfaces may also be modified by simple chemical protocols to attachspecific peptides or to immobilize proteins to elicit selective cellularresponses in tissue engineering applications or in implant design.

Controlled drug delivery systems may also be prepared, in which abiologically or pharmaceutically active agent is physically embedded ordispersed into the polymeric matrix, physically admixed with, orcovalently bonded to the aromatic polyanhydride. Covalent bonding isaccomplished by providing an aromatic polyanhydride having reactivefunctional groups on one or more Ar groups or R moieties and reactingthe polyanhydride with a derivatized or underivatized biologically orpharmaceutically active compound capable of reacting with the functionalgroup on the aromatic polyanhydride to form a covalent bond. Thus,biologically or pharmaceutically active compounds may be linked toaromatic polyanhydrides by means of ester groups, amide groups, and thelike.

Examples of biologically or pharmaceutically active compounds suitablefor the use in the present invention include acyclovir, cephradrine,malphalan, procaine, ephedrine, adriamicin, daunomycin, plumbagin,atropine, quinine, digoxin, quinidine, biologically active peptides,chlorin e₆, cephadrine, cephalothin, penicillin IV, nicotinic acid,chemodeoxycholic acid, chlorambucil, and the like. Biologically activecompounds, for the purposes of the present invention, are additionallydefined as including cell mediators, biologically active ligands, andthe like. The compounds are covalently bonded to the aromaticpolyanhydride by methods well understood by those of ordinary skill inthe art. Drug delivery compounds may also-be formed by physicallyblending the biologically or pharmaceutically active compound to bedelivered with the aromatic polyanhydrides of the present inventionusing conventional techniques well-known to those of ordinary skill inthe art.

The following non-limiting examples set forth hereinbelow illustratecertain aspects of the invention. All parts and percentages are byweight unless otherwise noted and all temperatures are in degreesCelsius. Except for acetic anhydride and ethyl ether (FisherScientific), all solvents and reagents were obtained from AldrichChemical. All solvents were HPLC grade. All other reagents were ofanalytical grade and were purified by distillation or recrystallization.

All compounds were characterized by a proton nuclear magnetic resonance(NMR) spectroscopy, infrared (IR) spectroscopy, gel permeationchromatography (GPC), high performance liquid chromatography (HPLC),differential scanning calorimetry (DSC), and thermal gravimetricanalysis (TGA). Infrared spectroscopy was performed on an AT1 MattsonGenesis (M100) FTIR Spectrophotometer. Samples were prepared by solventcasting on NaCl plates. ¹H and ¹³C NMR spectroscopy was obtained on aVarian 200 MHz or Varian 400 MHz spectrometer in solutions of CDCl₃ orDMSO-d₆ with solvent as the internal reference.

GPC was performed on a Perkin-Elmer Advanced LC Sample Processor (ISS200) with PE Series 200 LC Pump and a PE Series LC Refractive IndexDetector to determine molecular weight and polydispersity. The dataanalysis was carried out using Turbochrom 4 software on a DEC Celebris466 computer. Samples were dissolved in tetrahydrofuran and elutedthrough a mixed bed column (PE PL gel, 5 μm mixed bed) at a flow rate of0.5 mL/min. Samples (about 5 mg/mL) were dissolved into thetetrahydrofuran and filtered using 0.5 μm PTFE syringe filters prior tocolumn injection. Molecular weights were determined relative to narrowmolecular weight polystyrene standards (Polysciences, Inc.).

Thermal analysis was performed on a Perkin-Elmer system consisting of aTGA 7 thermal gravimetric analyzer equipped with PE AD-4 autobalance andPyris 1 DSC analyzer. Pyris software was used to carry out data analysison a DEC Venturis 5100 computer. For DSC, an average sample weight of5-10 mg was heated at 10° C./min. at a 30 psi flow of N₂. For TGA, anaverage sample weight of 10 mg was heated at 20° C./min under a 8 psiflow of N₂. Sessile drop contact angle measurements were obtained withan NRL Goniometer (Rame-hart) using distilled water. Solutions ofpolymer in methylene chloride (10% wt/vol.) were spun-coated onto glassslips, at 5,000 rpm for 30 seconds.

EXAMPLES Example I Preparation of 1,6-Bis(o-Carboxyphenoxy)HexaneDicarboxylic Acid

To a mixture of salicylic acid (77.12 g, 0.5580 mole) and distilledwater (84 mL) sodium hydroxide (44.71 g, 1.120 mole) was added. Thereaction was brought to reflux temperature before 1,6-dibromohexane(45.21 g, 0.2790 mole) was added drop-wise. Reflux was continued for 23hours after which additional sodium hydroxide (11.17 g, 0.2790 mole) wasadded. The mixture was refluxed for 16 more hours, cooled, filtered, andwashed with methanol. The yield-was 48.8%.

Example II Preparation of 1,6-Bis(o-Carboxyphenoxy)Hexane Monomer(o-CPH)

The dicarboxylic acid of Example I was acetylated in an excess of acidicanhydride at reflux temperature. The resulting monomer was precipitatedfrom methylene chloride into an excess of diethyl ether. The yield was66.8%.

Example III Preparation of Poly(1,6-Bis(o-Carboxyphenoxy)Hexane)(Poly(o-CPH))

The monomer of Example II was polymerized in a melt condensationperformed at 180° C. for 3 hours under vacuum in a reaction vessel witha side arm. The polymerization vessel was flushed with nitrogen atfrequent intervals. The polymer was isolated by precipitation intodiethyl ether from methylene chloride. The yield was quantitative.

All compounds were characterized by nuclear magnetic resonancespectroscopy, GPC, differential scanning calorimetry (DSC), thermalgravimetric analysis, contact angle measurements, UV spectroscopy, massspectroscopy, elemental analysis and high pressure liquid chromatography(HPLC).

The o-CPH monomer was polymerized by melt polycondensation for 60minutes at temperatures ranging from 100° to 300° C. Analysis of theresulting polymers by GPC indicated that the highest molecular weight,coupled with the lowest polydispersity index occurred at 260° C.

The poly(o-CPH) was generally soluble in methylene chloride andchloroform, while the poly(p-CPH) was not. The poly(o-CPH) was slightlysoluble in tetrahydrofuran, acetone and ethyl acetate.

Disks of poly(o-CPH), poly(p-CPH) and, as a reference, poly(lactic acidglycolic acid) were prepared and placed in 0.1 phosphate buffer solutionat 37° C. for 4 weeks. The degradation media was replaced periodically.The degradation profile was linear up to three weeks time.

In currently used polyanhydride systems, the aromatic groups arepara-substituted. This substitution pattern results in higher melt andglass transition temperatures and decreased solubility, thus ultimatelymaking these para-substituted polymers difficult to process.

Poly(o-CPH), unlike poly(p-CPH), has both a lower melting point (65° C.vs. 143° C.) and glass transition temperature (35° C. vs. 47° C.). It isalso possible to solution cast poly(o-CPH) using low-boiling solventswhereas poly(p-CPH) is relatively insoluble in most organic and aqueoussolvents. This structural modification gives a polymer whose hydrolysisproducts are chemically similar to aspirin. Aspirin is ananti-inflammatory agent derived from salicylic acid, which is one of thereagents used to synthesize the inventive polyanhydrides. Therefore, thedegradation products of this polymer may actually aid in patientrecovery. Because of pliability and ease of processing, the aromaticpolyanhydrides of the present invention have great potential as polymerscaffolds for wound healing.

Example IV Preparation of 1,3-bis o-carboxyphenoxy)propane dicarboxylicAcid

1,3-dibromopropane (14.7 mL, 0.145 mole) was added to a mixture ofsalicylic acid (40.0 g, 0.290 mole), distilled water (44 mL) and sodiumhydroxide (23.2 g, 0.580 mole) using the method described in Example I.After 4 hours, additional sodium hydroxide (5.79 g, 0.145 mole) wasadded to the reaction mixture. Reflux was continued for another 4 hours,after which the mixture was cooled, filtered and washed using themethods described in Example I. The yield was 37.7%

Example V Preparation of poly(1,3-bis(o-carboxyphenoxy)propane)

The dicarboxylic acid of Example IV was acetylated using the methods ofExample II. The acetylated dicaboxylic acid was then polymerized usingthe methods described in Example III. The resulting polymer had a M_(w)of 8,500 daltons and a polydispersity of 2.3.

Contact angle measurements on solvent-cast films demonstrated that thehexyl chain of the polymer of Example III increased the surfacehydrophobicity relative to the shorter propyl chain of the polymer ofExample V. A comparison of thermal characteristics emphasized theeffects of lengthening the alkyl chain. In particular, the polymer ofExample III has a T_(g) of 34° C. and a T_(d) of 410° C., while thepolymer of Example V had a T_(g) of 50° C. and a T_(d) of 344° C. Thus,the hexyl chain decreased the glass transition temperature (T_(g))relative to the propyl chain, reflecting the increased flexibility ofthe polymer chain. The opposite trend was observed for decompositiontemperatures (T_(d)), with the longer alkyl chain increasing the T_(d).

Optimum polycondensation conditions were determined for the polymer ofExample III. Optimum conditions were defined as those that yielded acrude polymer with the highest molecular weight and highest T_(g).Higher reaction temperatures decreased the M_(w) values (measured byGPC) with a concurrent increase in polydispersity. As expected for acondensation polymerization, longer reaction times yielded polymers withhigher molecular weights. However, over longer reaction times, thereappeared a subsequent decrease in T_(g). Based on these results, theoptimum conditions were defined as temperatures of 220° C. for 150minutes under a vacuum.

Example VI Preparation of 1,8-bis[o-(benzylcarboxy)carboxyphenyl] octanedicarboxylic Acid Ester

The initial synthesis of poly(anhydride-ester)dicarboxylic acid monomerswas attempted using the same methodology used for thepoly(anhydride-ether)dicarboxylic monomers of Example III. It was found,however, that the reactivity of the phenol was enhanced by benzylationof the carboxylic acid group. In addition, the solubility of benzylsalicylate in organic media increased the ability of the reaction tomove forward.

Thus, benzyl salicylate (1.530 g, 6.720 mmole) and distilledtetrahydrofuran were combined under an inert atmosphere in a reactionflask. An ice-salt bath was placed under the reaction flask and theaddition of 60% sodium hydride (0.4840 g, 12.10 mmole) followed. Afterone hour, sebacoyl chloride (0.7850 g, 3.280 mmole) was added drop-wiseto the 0° C. reaction mixture. After 30 minutes, the reaction mixturewas vacuum filtered, the filtrate collected and the solvent removed toreveal to yield the free carboxylate as a white solid residue.Purification was performed using a chromatron with ethylacetate/methylene chloride (20/80) as the solvent system. The yield was43%.

Example VII Polymerization of Poly(1,8-bis(o-dicarboxyphenyl)octane)

To remove the benzyl protecting groups, the1,8-bis[(benzylcarboxy)carboxyphenyl]octane dicarboxylic acid ester ofExample VI (0.06000 g, 0.9620 mmole) was dissolved in methylene chloridein a reaction flask (60.00 mL). The catalyst Pd—C (10%, 1.200 g) wasadded to the reaction flask. After 30 minutes, the reaction wascomplete. The reaction mixture was filtered and the solvent removed toyield the free dicarboxylic acid as a white solid residue which wasrecrystallized using petroleum ether and methylene chloride. The yieldwas 45%.

The dicarboxylic acid was acetylated using the methods described inExample II and the acetylated dicarboxylic acid was then polymerizedusing the methods described in Example III. The resulting polymer had aM_(w) of 3,000 daltons and a polydispersity of 1.40.

Subsequent polymerizations yielded polymers with MY's ranging from 2,000to 5,000 daltons with corresponding polydispersities of approximately1.40.

The poly(anhydride esters) of Example VII were compression molded intocircular discs and placed in phosphate buffered saline solution underacidic, neutral and basic conditions. Over the course of a three-weekdegradation study, the polymers in the acidic and neutral solutionsshowed no observable changes, whereas the polymer in the basic mediashowed significant morphological changes over time.

Example VIII Preparation of Poly[(1,8-biso-dicarboxyphenyl)octane)-(1,6-bis(p-carboxyphenoxy)hexane]copolymers

The 1,8-bis(o-dicarboxyphenyl)octane of Example II was copolymerizedwith 1,6-bis(p-carboxyphenoxy)hexane using the methods described inExample III. In an in vivo mouse study, each mouse was implanted with 2polymers, the copolymer of Example VIII andpoly(1,6-bis(p-carboxyphenoxy)hexane). Each polymer was compressionmolded for 1 to 5 minutes at 1 to 20 K psi depending on the thickness ofpolymer needed. The polymer was placed under the palatal gingival mucosaadjacent to the first maxillary molars. The mice were sacrificed at 1, 4and 10 day intervals and demonstrated the biocompatibility anbiodegradability in vivo of the polymers of the present invention, withsalicylic acid being released upon degradation, via hydrolysis of thepolymer backbone.

STATEMENT OF INDUSTRIAL APPLICABILITY

The polymers of the present invention have a variety of pharmaceuticalapplications, particularly as anti-inflammatory compounds.

The foregoing examples and description of the preferred embodimentshould be taken as illustrating, rather than as limiting, the presentinvention as defined by the claims. As would be readily appreciated,numerous variations and combinations of the features set forth above canbe utilized without departing from the present invention as set forth inthe claims. Such variations are not regarded as a departure from thespirit and the scope of the invention, and all such variations areintended to be included within the scope of the following claims.

1. An aromatic polyanhydride comprising a repeating unit having thestructure:

wherein R is -Z₁-R₁-Z₁- substituted on each Ar ortho to the anhydridegroup; R₁ is a difunctional organic moiety; each Z₁ is a difunctionalmoiety selected from the group consisting of esters, carbamates andcarbonates; and Ar is selected so that the aromatic polyanhydride canhydrolyze to form salicylic acid.
 2. A drug delivery system comprisingthe aromatic polyanhydride of claim 1 physically admixed with abiologically or pharmaceutically active agent.
 3. A drug delivery systemcomprising a biologically or pharmaceutically active agent physicallyembedded or dispersed into a polymeric matrix formed from the aromaticpolyanhydride of claim
 1. 4. A drug delivery system comprising abiologically or pharmaceutically active agent covalently bonded to thearomatic polyanhydride of claim
 1. 5. An implantable medical devicecomprising the aromatic polyanhydride of claim
 1. 6. The implantablemedical device of claim 5, wherein said device is a scaffolding implantfor tissue reconstruction.
 7. A method for site-specific or systemicdrug delivery comprising implanting in the body of a patient in needthereof an implantable drug delivery device comprising a therapeuticallyeffective amount of the aromatic polyanhydride of claim
 1. 8. A methodfor treating inflammation comprising administering to a patient in needthereof an effective amount of the aromatic polyanhydride of claim
 1. 9.The method of claim 8, wherein the aromatic polyanhydride isadministered orally.
 10. The method of claim 8, wherein the inflammationis digestive inflammation.
 11. The method of claim 8, wherein theinflammation is caused by a digestive disorder.
 12. The method of claim11, wherein the digestive disorder is a bowel disorder.
 13. The methodof claim 11, wherein the digestive disorder is an inflammatory boweldisease.
 14. The method of claim 11, wherein the digestive disorder isCrohn's disease.
 15. A dosage form comprising an effective amount of thearomatic polyanhydride of claim 1 and a pharmaceutically acceptableexcipient.
 16. The dosage form of claim 15 that is an oral dosage form.17. The aromatic polyanhydride of claim 1, wherein each Z₁ is adifunctional moiety selected from the group consisting of esters, andcarbamates.
 18. The aromatic polyanhydride of claim 1, wherein R₁ isselected from the group consisting of (—CH₂—CH₂—O—)_(m),(—CH₂—CH₂—CH₂—O—)_(m), and (—CH₂—CHCH₃—O—)_(m), wherein m is selected sothat R₁ has between 2 and 20 carbon atoms, inclusive.
 19. The aromaticpolyanhydride of claim 1, wherein R₁ is (—CH₂—)_(n), wherein n is from 1to 20, inclusive.
 20. The aromatic polyanhydride of claim 1, whereineach Z₁ is an ester.
 21. The aromatic polyanhydride of claim 19, whereineach Z₁ is an ester.
 22. The aromatic polyanhydride of claim 20, whereinn is
 6. 23. The aromatic polyanhydride of claim 21, wherein n is
 6. 24.The aromatic polyanhydride of claim 20, wherein n is
 8. 25. The aromaticpolyanhydride of claim 21, wherein n is 8.